Dog: Does anyone know what this is?

I have a 9 month old Doberman and this isn't the first time he's had this. Last time it went away. When they pop, puss and hair comes out. Are they ingrown hairs? Should I take him to the vet for this? I have a Labrador as well and he's never had this before. They're really thick when you touch them and I think they hurt him. 
Also, no I don't pop them. They pop on their own and sometimes when my two dogs play too rough they will bleed.